CN111755320A - Polysilicon functional film, preparation method and application thereof - Google Patents
Polysilicon functional film, preparation method and application thereof Download PDFInfo
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Abstract
The invention discloses a polysilicon functional film, a preparation method and application thereof, belonging to the technical field of semiconductor preparation, wherein the preparation method comprises the following steps: providing a pretreated silicon-based substrate; forming a silicon dioxide oxide layer on the substrate; after alkali washing treatment is carried out on the substrate containing the oxide layer, the substrate is heated to a deposition temperature; then exposing the substrate to at least one group IV precursor to grow a polycrystalline silicon thin film; the pretreatment of the silicon-based substrate comprises a pulse cleaning step; the pulse cleaning is carried out for 20-30 cycles, the pulse time is 0.1-0.2s, and the cleaning time is 4-5 s. The preparation method of the polysilicon functional film provided by the invention can reduce the surface roughness of the substrate, improve the surface roughness and the flatness of the polysilicon film, shorten the nucleation incubation period of polysilicon deposition, improve the deposition growth rate of an oxide layer and the polysilicon film, control the warping degree of the polysilicon film and the substrate, improve the yield and the yield, and reduce the production loss and the cost.
Description
Technical Field
The invention belongs to the technical field of semiconductor preparation, and particularly relates to a polycrystalline silicon functional film, a preparation method and application thereof.
Background
Polysilicon is a form of elemental silicon, and a polysilicon material is a polycrystalline material composed of silicon grains. The properties of the polysilicon film depend on the grain size, the height of the grain boundary barrier, the arrangement of crystal planes and the surface state. The polycrystalline silicon thin film material has the advantages of high mobility of monocrystalline silicon material and large-area and low-cost preparation of amorphous silicon material. Therefore, attention is being drawn to the research on the polysilicon thin film material, which has photosensitivity in a long wavelength band and visible light sensitivityThe polycrystalline silicon film can be effectively absorbed and has illumination stability, so that the polycrystalline silicon film is a high-efficiency and low-energy-consumption photovoltaic device material, and has great potential in application to solar cells. Meanwhile, the polycrystalline silicon thin film material has high mobility which can reach 390cm2the/V · S, close to the mobility of single crystalline silicon materials, is widely used in some semiconductor devices. In recent years, the polysilicon thin film material has the advantages of large area, low cost and high carrier mobility, so that the polysilicon thin film material has more and more important application value in the aspect of large-area microelectronic devices, and the technology of manufacturing the polysilicon thin film material into the thin film transistor plays an important role in the fields of integrated circuits and large-array liquid crystal display devices. It is widely used in integrated circuits as the gate of a self-aligned insulated gate common effect transistor (MOSFET), the floating gate of a flash memory, the emitter of a triode, the plate of a capacitor, a resistor, an interconnection material and the like.
Polysilicon is an important material in semiconductor devices and their manufacture, and polysilicon thin films are important structures in semiconductor devices. At present, the preparation of the polycrystalline silicon film mainly comprises two types: firstly, a polysilicon film is generated on a substrate in one step by adopting a chemical vapor deposition method, for example, silicon source gas is decomposed under the condition of gas phase and is deposited on the substrate at high temperature to form the polysilicon film. Common chemical vapor deposition techniques include low pressure chemical vapor deposition, atmospheric pressure chemical vapor deposition, plasma enhanced chemical vapor deposition, and hot filament chemical vapor deposition: the temperature is generally over 600 ℃ in the preparation process, the substrate can only be made of expensive quartz or silicon wafers, the device manufacturing and substrate selection are limited, and the precursor SiH4The adsorption on the silicon surface is slow, so that the whole reaction speed is limited, but the preparation process is relatively simple. Secondly, firstly growing an amorphous silicon film on the substrate, and then crystallizing the amorphous silicon to obtain a polycrystalline silicon film through post-treatment: the temperature of the whole preparation process is lower than 600 ℃, and cheap glass can be used as a substrate by adopting a low-temperature process, so that the preparation process can be carried out in a large area, but the preparation process is relatively complex and the equipment is expensive. Therefore, the preparation method of the polycrystalline silicon functional film with high growth efficiency and high quality is of great significance.
Disclosure of Invention
The invention aims to provide a preparation method of a polysilicon functional film, which can reduce the surface roughness of the substrate, improve the surface roughness and the flatness of a polysilicon film, shorten the nucleation incubation period of polysilicon deposition, improve the deposition growth rate of an oxide layer and the polysilicon film, control the warping degree of the polysilicon film and the substrate, improve the yield and the yield, and reduce the production loss and the cost.
The technical scheme adopted by the invention for realizing the purpose is as follows:
a preparation method of a polysilicon functional film comprises the following steps: providing a pretreated silicon-based substrate; forming a silicon dioxide oxide layer on the substrate; after alkali washing treatment is carried out on the substrate containing the oxide layer, the substrate containing the oxide layer is heated to a deposition temperature; then exposing the substrate containing the oxidation layer to at least one IV group precursor, and growing a polycrystalline silicon film by adopting an LPCVD process;
wherein, the pretreatment of the silicon-based substrate comprises a pulse cleaning step; the pulse cleaning is carried out for 20-30 cycles, the pulse time is 0.1-0.2s, and the cleaning time is 4-5 s.
Method for growing polycrystalline silicon film by conventional LPCVD process, precursor SiH4The adsorption on the silicon surface is slow, and when the crystal grain size is increased, the electrical properties of the polysilicon film are easily adversely affected along with the increase in surface roughness. The preparation method provided by the invention can reduce the surface roughness of the substrate, shorten the nucleation incubation period of the polysilicon deposition, improve the deposition growth rate of the polysilicon, improve the yield and the yield, and reduce the production loss and the cost; the obtained polysilicon functional film has compact surface, high brightness, low roughness and high flatness, has high in-chip thickness uniformity, and reduces the loss rate in the subsequent etching and other processing operations.
For the present invention, in the above-mentioned pulse cleaning step, the pulse medium is tetraethoxysilane, and the cleaning medium is NH4F. HF, potassium fluotitanate and neodymium sulfate to prepare a solution with the pH value of 4.5-5. The pulse cleaning can further improve the surface cleanliness of the substrate and avoid the occurrence of polysilicon filmsThe surface fog phenomenon is used for improving the yield, in addition, the smoothness of the surface of the substrate is high through pulse cleaning, the steric hindrance effect between the precursor and the substrate is relatively reduced, the retention layer of precursor reactant molecules on the surface is thinned, the time for the reactant molecules to reach the surface of the substrate is shortened, the early nucleation incubation time of the reactant can be shortened, and the growth deposition rate of an oxide layer and a polycrystalline silicon film can be accelerated; and the smoothness of the substrate is improved, so that the increase of the surface roughness of the oxide layer can be inhibited while the deposition of crystal grains and the thickness of a thin film are increased, the surface roughness and the surface flatness of the polycrystalline silicon film are improved, the polycrystalline silicon film with low surface roughness and high flatness is obtained, the quality and the yield of products are improved, and the production loss and the cost are reduced.
Preferably, NH in the cleaning medium4F. The weight ratio of HF, potassium fluotitanate and neodymium sulfate is 10:10:0.1-0.3: 0.1-0.5.
Preferably, in the pulse cleaning step, the temperatures of the pulse medium and the cleaning medium are 120-180 ℃, and the substrate temperature is 200-350 ℃. More preferably, the pre-treatment of the silicon-based substrate comprises: firstly, the substrate is cleaned by an RCA method in wet cleaning, and then a pulse cleaning step is carried out.
For the purposes of the present invention, examples of silicon-based substrates are not limited to silicon, germanium, silicon carbide, or the like, or silicon-on-insulator (SOI), or gallium arsenide, or the like, and further, are not limited to undoped or lightly P-type doped silicon substrates.
For the purposes of the present invention, the formation of the silicon dioxide oxide layer includes, but is not limited to: an Atmospheric Pressure Chemical Vapor Deposition (APCVD) method, and a Low Pressure Chemical Vapor Deposition (LPCVD) method and a thermal oxidation method are used. The silicon dioxide oxide layer is different from the charge distribution of a silicon substrate after alkali cleaning treatment, the nucleation stage time during deposition of the polycrystalline silicon film can be shortened, the substrate damage caused by diffusion of polycrystalline silicon into the substrate can be prevented, and the phenomenon of low yield caused by deposition of the polycrystalline silicon layer after the deposition layer is formed on the surface of the substrate by the precursor is avoided.
For the present invention, the alkaline washing step is: carrying out ultrasonic auxiliary cleaning by using SPM cleaning solution, SC-1 cleaning solution and SC-2 cleaning solution step by step, and then drying by using pure nitrogen for later use; the ultrasonic power is 800-1500W. The alkaline washing treatment can effectively reduce various pollution sources existing on the surface of the silicon dioxide oxide layer, shorten the incubation period of the deposition of the polycrystalline silicon film, and avoid the influence of pinholes, bulges and the like caused by impurities in the polycrystalline silicon on the quality and the yield of products.
Preferably, the SPM cleaning solution is a mixed solution of sulfuric acid and hydrogen peroxide in a molar ratio of 1:4-6, and the temperature is 100-120 ℃; the SC-1 cleaning solution is a mixed solution of ammonia water, hydrogen peroxide and water with the molar ratio of 1:1-2:5-15, and the temperature is 80-100 ℃; the SC-2 cleaning solution is a mixed solution of hydrochloric acid, hydrogen peroxide and water with the molar ratio of 1:1-1.5:5-10, and the temperature is 70-90 ℃.
For the present invention, heating the substrate containing the oxide layer to the deposition temperature is heating the substrate to 350-.
For the present invention, the LPCVD process conditions are: the pressure is 25-75Pa, the deposition temperature Td is 600-650 deg.C, and the precursor flow rate is 300-1500 sccm.
For the invention, the preparation method also comprises the steps of carrying out heat treatment on the polycrystalline silicon film prepared by the LPCVD process; the operation steps of the heat treatment are as follows: heating to 950-1040 ℃ at the speed of 150-200 ℃/min, and then annealing for 60-75 min. The annealing treatment can change and release the interfacial stress among the substrate, the oxide layer and the polysilicon functional film layer, thereby effectively controlling and improving the warping degree of the functional film and the substrate and improving the quality of the functional film.
The invention also aims to provide the polycrystalline silicon functional film prepared by the preparation method. The polycrystalline silicon functional film has good consistency, uniform thickness distribution, improved surface flatness, low surface roughness, high yield and yield, and effectively controlled and improved production loss, cost and subsequent processing loss rate.
For the present invention, the thickness of the polysilicon functional film prepared by the above preparation method is as follows
The thickness of the polysilicon functional film is smallThe degree uniformity is not higher than 1.5%.
The invention also aims to provide application of the polycrystalline silicon functional film prepared by the preparation method in preparing electronic devices.
The invention adopts the preparation method of pulse cleaning of the silicon-based substrate, oxide layer growth and polysilicon deposition functional film deposition on the substrate, thereby having the following beneficial effects: 1) the preparation method can reduce the surface roughness of the substrate, shorten the nucleation incubation period of the polysilicon deposition, improve the deposition growth rate of the oxide layer and the polysilicon film, improve the surface roughness and the surface smoothness of the polysilicon film, improve the yield and the yield, and reduce the production loss and the cost; 2) the obtained polysilicon functional film has compact surface, high brightness, low roughness, high flatness, few phenomena of pinholes, bulges and the like caused by impurities, high in-chip thickness uniformity, high yield and yield, controlled warping degree of the polysilicon film and the substrate, and reduced loss rate in subsequent etching and other processing operations; 3) the obtained polysilicon functional film has excellent electrical properties and can be used as a core element in an electronic device.
Therefore, the invention is a preparation method of the polysilicon functional film and the application thereof in preparing electronic devices, wherein the preparation method can reduce the surface roughness of the substrate, improve the surface roughness and the flatness of the polysilicon film, shorten the nucleation incubation period of polysilicon deposition, improve the deposition growth rate of an oxide layer and the polysilicon film, control the warping degree of the polysilicon film and the substrate, and reduce the production loss and the cost.
Drawings
Fig. 1 is a schematic diagram of warp changes before and after a polysilicon functional film and a silicon-based substrate in different preparation methods.
Detailed Description
The technical solution of the present invention is further described in detail below with reference to the following detailed description and the accompanying drawings:
a preparation method of a polysilicon functional film comprises the following steps: providing a pretreated silicon-based substrate; forming a silicon dioxide oxide layer on the substrate; after alkali washing treatment is carried out on the substrate containing the oxide layer, the substrate containing the oxide layer is heated to a deposition temperature; then exposing the substrate containing the oxidation layer to at least one IV group precursor, and growing a polycrystalline silicon film by adopting an LPCVD process;
wherein, the pretreatment of the silicon-based substrate comprises a pulse cleaning step; the pulse cleaning is carried out for 20-30 cycles, the pulse time is 0.1-0.2s, and the cleaning time is 4-5 s.
Method for growing polycrystalline silicon film by conventional LPCVD process, precursor SiH4The adsorption on the silicon surface is slow, and when the crystal grain size is increased, the electrical properties of the polysilicon film are easily adversely affected along with the increase in surface roughness. The preparation method provided by the invention can reduce the surface roughness of the substrate, shorten the nucleation incubation period of the polysilicon deposition, improve the deposition growth rate of the polysilicon, improve the yield and the yield, and reduce the production loss and the cost; the obtained polysilicon functional film has compact surface, high brightness, low roughness and high flatness, has high in-chip thickness uniformity, and reduces the loss rate in the subsequent etching and other processing operations.
For the present invention, in the above-mentioned pulse cleaning step, the pulse medium is tetraethoxysilane, and the cleaning medium is NH4F. HF, potassium fluotitanate and neodymium sulfate to prepare a solution with the pH value of 4.5-5. The pulse cleaning can further improve the cleanliness of the surface of the substrate, avoid the surface fog phenomenon of the polycrystalline silicon film so as to improve the yield, and ensure that the smoothness of the surface of the substrate is high through the pulse cleaning, the steric hindrance effect between the surface of the substrate and a precursor is relatively reduced, so that a retention layer of precursor reactant molecules on the surface is thinned, the time for the reactant molecules to reach the surface of the substrate is shortened, the early nucleation incubation time of the reactant can be shortened, and the growth deposition rate of an oxide layer and the polycrystalline silicon film can be accelerated; and the smoothness of the substrate is improved, so that the increase of the surface roughness of the oxide layer can be inhibited while the deposition of crystal grains and the thickness of a thin film are increased, the surface roughness and the surface flatness of the polycrystalline silicon film are improved, the polycrystalline silicon film with low surface roughness and high flatness is obtained, the quality and the yield of products are improved, and the production loss and the cost are reduced.
Preference is given toOf NH in the cleaning medium4F. The weight ratio of HF, potassium fluotitanate and neodymium sulfate is 10:10:0.1-0.3: 0.1-0.5. Preferably, in the pulse cleaning step, the temperatures of the pulse medium and the cleaning medium are 120-180 ℃, and the substrate temperature is 200-350 ℃. More preferably, the pre-treatment of the silicon-based substrate comprises: firstly, the substrate is cleaned by an RCA method in wet cleaning, and then a pulse cleaning step is carried out.
For the purposes of the present invention, examples of silicon-based substrates are not limited to silicon, germanium, silicon carbide, or the like, or silicon-on-insulator (SOI), or gallium arsenide, or the like, and further, are not limited to undoped or lightly P-type doped silicon substrates.
For the purposes of the present invention, the formation of the silicon dioxide oxide layer includes, but is not limited to: an Atmospheric Pressure Chemical Vapor Deposition (APCVD) method, and a Low Pressure Chemical Vapor Deposition (LPCVD) method and a thermal oxidation method are used. The silicon dioxide oxide layer is different from the charge distribution of a silicon substrate after alkali cleaning treatment, the nucleation stage time during deposition of the polycrystalline silicon film can be shortened, the substrate damage caused by diffusion of polycrystalline silicon into the substrate can be prevented, and the phenomenon of low yield caused by deposition of the polycrystalline silicon layer after the deposition layer is formed on the surface of the substrate by the precursor is avoided.
For the present invention, the alkaline washing step is: carrying out ultrasonic auxiliary cleaning by using SPM cleaning solution, SC-1 cleaning solution and SC-2 cleaning solution step by step, and then drying by using pure nitrogen for later use; the ultrasonic power is 800-1500W. The alkaline washing treatment can effectively reduce various pollution sources existing on the surface of the silicon dioxide oxide layer, shorten the incubation period of the deposition of the polycrystalline silicon film, and avoid the influence of pinholes, bulges and the like caused by impurities in the polycrystalline silicon on the quality and the yield of products.
Preferably, the SPM cleaning solution is a mixed solution of sulfuric acid and hydrogen peroxide in a molar ratio of 1:4-6, and the temperature is 100-120 ℃; the SC-1 cleaning solution is a mixed solution of ammonia water, hydrogen peroxide and water with the molar ratio of 1:1-2:5-15, and the temperature is 80-100 ℃; the SC-2 cleaning solution is a mixed solution of hydrochloric acid, hydrogen peroxide and water with the molar ratio of 1:1-1.5:5-10, and the temperature is 70-90 ℃.
Preferably, the ultrasound-assisted cleaning operation is: ultrasonically cleaning the substrate containing the oxide layer for 3-5min by using SPM cleaning solution, ultrasonically cleaning for 5-6min by using SC-1 cleaning solution, repeating for 2 times, washing for 1min by using deionized water in the middle, and ultrasonically cleaning for 3-5min by using SC-2 cleaning solution.
In a more preferable embodiment, in the alkaline cleaning step, after cleaning of the substrate containing the oxide layer by the SPM cleaning solution, the SC-1 cleaning solution and the SC-2 cleaning solution is completed, an etching cleaning step is further performed, and then pure nitrogen is used for blow-drying for later use; the etching and cleaning operations are as follows: adopting 800-1500W ultrasonic wave assistance power, etching and cleaning the substrate containing the oxide layer for 10-30s at the temperature of 70-90 ℃ in the presence of ammonium fluorosilicate and potassium bromate, wherein the weight percentages of the ammonium fluorosilicate and the potassium bromate in an etching medium are respectively 0.01-0.05% and 0.03-0.1%, and the etching medium also comprises 2-5 wt% of hydrofluoric acid. Reducing interface traps in the boundary of an oxide layer by ultrasonic energy in the presence of ammonium fluosilicate and potassium bromate, and weakening the condition of nonuniform deposition thickness caused by the difference of air flow at the center and the edge of a substrate, particularly when the thickness of a film is
In the process, the uniformity of the thickness in the wafer can be controlled to be not higher than 1%, the diameter of the crystal grains is prevented from being increased unevenly and the surface roughness is prevented from being increased rapidly due to the increase of the diameter of the silicon film, the uniformity of the size and the distribution of the crystal grains is improved, and the loss rate in the subsequent processing operation is reduced; meanwhile, the diffusion of reactants on the surface of the oxide layer can be increased, so that the defects and dislocation in the deposited film are reduced, the film becomes compact, the free energy and stress between interfaces are released, the warping degree of the polycrystalline silicon film and the substrate is reduced, the warping degree of the polycrystalline silicon functional film with the diameter of 100-200mm can be controlled below 5 mu m, and the quality of the product functional film is improved.
For the present invention, heating the substrate containing the oxide layer to the deposition temperature is heating the substrate to 350-.
For the purposes of the present invention, the group IV precursor is Silane (SiH)4) Disilane (Si)2H6) Trisilane (Si)3H8) Butyl silane (Si)4H10) IsopreneSilane (Si)5H12) Neopentasilane (Si)5H12) Dichlorosilane (DCS), methylsilane (CH)3-SiH3) At least one of (1). Preferably, the group IV precursor is Silane (SiH)4) And disilane (Si)2H6)。
For the present invention, the LPCVD process conditions are: the pressure is 25-75Pa, the deposition temperature Td is 600-650 deg.C, and the precursor flow rate is 300-1500 sccm.
For the invention, the preparation method also comprises the steps of carrying out heat treatment on the polycrystalline silicon film prepared by the LPCVD process; the operation steps of the heat treatment are as follows: heating to 950-1040 ℃ at the speed of 150-200 ℃/min, and then annealing for 60-75 min. The annealing treatment can change and release the interfacial stress among the substrate, the oxide layer and the polysilicon functional film layer, thereby effectively controlling and improving the warping degree of the functional film and the substrate and improving the quality of the functional film.
The invention also provides a polysilicon functional film prepared by the preparation method. The polycrystalline silicon functional film has good consistency, uniform thickness distribution, improved surface flatness, low surface roughness, high yield and yield, and effectively controlled and improved production loss, cost and subsequent processing loss rate.
For the present invention, the thickness of the polysilicon functional film prepared by the above preparation method is as follows
And in the process, the uniformity of the thickness of the polycrystalline silicon functional film in the wafer is not higher than 1.5 percent.
The invention also provides application of the polycrystalline silicon functional film prepared by the preparation method in preparing electronic devices.
The present invention and the conventional techniques in the embodiments are known to those skilled in the art and will not be described in detail herein.
It should be understood that the foregoing description is to be considered illustrative or exemplary and not restrictive, and that in particular the invention covers other embodiments having any combination of features from the different embodiments described above and below, without the scope of the invention being limited to the specific examples below.
Example 1:
a preparation method of a polysilicon functional film comprises the following specific steps:
1) cleaning a silicon-based substrate with deionized water, ethanol and acetone in sequence, heating the substrate to 250 ℃ after cleaning by a conventional RCA method, and then carrying out 25-cycle pulse cleaning on the substrate, wherein the pulse time is 0.1s, the pulse medium is tetraethoxysilane with the temperature of 160 ℃, the cleaning time is 5s, and the cleaning medium is NH4F. A solution with pH of 4.9 and temperature of 160 ℃ is prepared from HF, potassium fluotitanate and neodymium sulfate according to the weight ratio of 10:10:0.15: 0.15;
2) depositing an oxide layer with a thickness of 100nm, wherein SiH, by LPCVD4The flow is 15sccm, the hydrogen flow is 10sccm, the protective gas argon flow is 200sccm, the deposition temperature of the silicon film is 650 ℃, the deposition time is 20min, then oxygen is introduced into the silicon film for oxidation, the oxygen flow is 25sccm, the oxidation temperature is 600 ℃, and the oxidation time is 25min, so as to obtain a substrate containing oxide layer silicon dioxide;
3) after the temperature of the substrate is reduced to below 150 ℃, carrying out ultrasonic cleaning for 5min by using SPM cleaning solution at the temperature of 120 ℃, then carrying out ultrasonic cleaning for 5min by using SC-1 cleaning solution at the temperature of 90 ℃, repeating for 2 times, washing for 1min by using deionized water in the middle, carrying out ultrasonic cleaning for 5min by using SC-2 cleaning solution at the temperature of 80 ℃, and then carrying out blow-drying by using pure nitrogen for later use; wherein the ultrasonic power is 1000W, the SPM cleaning solution is a mixed solution of sulfuric acid and hydrogen peroxide with a molar ratio of 1:4.5, the SC-1 cleaning solution is a mixed solution of ammonia water, hydrogen peroxide and water with a molar ratio of 1:1:13, and the SC-2 cleaning solution is a mixed solution of hydrochloric acid, hydrogen peroxide and water with a molar ratio of 1:1.5: 9.5;
4) the substrate containing the oxidation layer is sent into a reaction chamber and heated to 550 ℃ at the heating rate of 150 ℃/min;
5) depositing polysilicon functional film by LPCVD method, with the IV group precursor being Si2H6Deposition pressure of 63Pa, deposition temperature Td of 630 deg.C, precursor flow of 750sccm, depositionThe product time is 90 min;
6) heating to 1000 ℃ at the speed of 150 ℃/min in protective gas, annealing for 65min, taking out after the polysilicon functional film is cooled to room temperature, and sealing for later use.
Example 2:
the preparation method of the polysilicon functional film has the specific steps basically the same as those of the embodiment 1, and the difference is only that
In the following steps: in the step 1), the silicon-based substrate is heated to 300 ℃, and then 30 cycles of pulse cleaning are carried out, wherein the cleaning medium is NH4F. A solution with pH of 4.7 and temperature of 180 ℃ is prepared from HF, potassium fluotitanate and neodymium sulfate according to the weight ratio of 10:10:0.3: 0.2;
in step 2), depositing an oxide layer with a thickness of 50nm, wherein SiH, by an LPCVD method4The flow rate is 20sccm, the hydrogen flow rate is 7.5sccm, the protective gas argon flow rate is 200sccm, the deposition temperature of the silicon film is 630 ℃, the deposition time is 15min, then oxygen is introduced into the silicon film for oxidation, the oxygen flow rate is 30sccm, the oxidation temperature is 600 ℃, and the oxidation time is 20min, so that the substrate containing the oxide layer silicon dioxide is obtained;
in the step 5), depositing the polysilicon functional film by LPCVD method, and selecting the IV group precursor as SiH4The deposition pressure is 65Pa, the deposition temperature Td is 650 ℃, the precursor flow is 500sccm, and the deposition time is 120 min;
and 6), heating to 1040 ℃ at a speed of 200 ℃/min in protective gas, annealing for 60min, taking out after the polysilicon functional film is cooled to room temperature, and sealing for later use.
Example 3:
the preparation method of the polysilicon functional film basically has the same concrete steps as the embodiment 1, and the difference is that:
in the step 1), the cleaning medium for pulse cleaning is NH4F. A solution with pH of 4.8 and temperature of 150 ℃ is prepared from HF, potassium fluotitanate and neodymium sulfate according to the weight ratio of 10:10:0.1: 0.5;
in the step 3), ultrasonically cleaning the substrate containing the oxide layer for 3min by using SPM cleaning liquid at the temperature of 100 ℃, ultrasonically cleaning the substrate for 6min by using SC-1 cleaning liquid at the temperature of 100 ℃, repeating the ultrasonic cleaning for 2 times, washing the substrate for 1min by using deionized water in the middle, ultrasonically cleaning the substrate for 3min by using SC-2 cleaning liquid at the temperature of 90 ℃, and drying the substrate by using pure nitrogen for later use; wherein the ultrasonic power is 1500W, the SPM cleaning solution is a mixed solution of sulfuric acid and hydrogen peroxide with a molar ratio of 1:6, the SC-1 cleaning solution is a mixed solution of ammonia water, hydrogen peroxide and water with a molar ratio of 1:2:15, and the SC-2 cleaning solution is a mixed solution of hydrochloric acid, hydrogen peroxide and water with a molar ratio of 1:1: 10;
in the step 4), the substrate containing the oxide layer is sent into a reaction chamber and heated to 600 ℃ at the heating rate of 100 ℃/min; in the step 5), depositing the polysilicon functional film by LPCVD method, and selecting the IV group precursor as Si2H6The deposition pressure is 70Pa, the deposition temperature Td is 650 ℃, the precursor flow is 900sccm, and the deposition time is 60 min;
and 6), heating to 980 ℃ at the speed of 150 ℃/min in protective gas, annealing for 70min, taking out after the temperature of the polysilicon functional film is reduced to room temperature, and sealing for later use.
Example 4:
the preparation method of the polysilicon functional film basically has the same concrete steps as the embodiment 1, and the difference is that:
in the step 3), after cleaning the substrate containing the oxide layer by SPM cleaning liquid, SC-1 cleaning liquid and SC-2 cleaning liquid, carrying out an etching cleaning step, and then blowing and drying the substrate by pure nitrogen for later use; the etching and cleaning operations are as follows: the substrate containing the oxide layer is subjected to etching cleaning for 10 seconds by adopting ultrasonic assistance with the power of 900W under the environment that the temperature is 90 ℃ and ammonium fluosilicate and potassium bromate exist, wherein the weight ratio of the ammonium fluosilicate to the potassium bromate in an etching medium is 0.025 percent and 0.075 percent respectively, and the etching medium also comprises 2.5 percent by weight of hydrofluoric acid.
Comparative example 1:
the preparation method of the polysilicon functional film basically has the same concrete steps as the embodiment 1, and the difference is that:
in the step 1), the pulse cleaning medium is NH4F. HF and potassium fluotitanate are mixed according to the weight ratio of 10:10:0.15, the pH value is 4.9, and the temperature is 160 ℃.
Comparative example 2:
the preparation method of the polysilicon functional film basically has the same concrete steps as the embodiment 1, and the difference is that:
in the step 1), the pulse cleaning medium is NH4F. HF and neodymium sulfate are prepared into a solution with pH of 4.9 and temperature of 160 ℃ according to the weight ratio of 10:10: 0.15.
Comparative example 3:
the preparation method of the polysilicon functional film basically has the same concrete steps as the embodiment 1, and the difference is that:
in the step 1), the pulse cleaning medium is NH4F. HF is prepared into a solution with pH of 4.9 and temperature of 160 ℃ according to the weight ratio of 1:1.
Comparative example 4:
the preparation method of the polysilicon functional film basically has the same concrete steps as the embodiment 1, and the difference is that:
in the step 1), the silicon-based substrate is cleaned by using deionized water, ethanol and acetone in sequence, and then cleaned by using a conventional RCA method for standby, and pulse cleaning operation is not carried out.
Comparative example 5:
the preparation method of the polysilicon functional film basically has the same specific steps as the embodiment 4, and the differences are that:
in the step 3), the etching and cleaning operations are as follows: and (2) carrying out etching cleaning on the substrate containing the oxide layer for 10s at 90 ℃ in the presence of ammonium fluorosilicate by adopting ultrasonic assistance with the power of 900W, wherein the weight ratio of the ammonium fluorosilicate in an etching medium is 0.025%, and the etching medium also comprises 2.5 wt% of hydrofluoric acid.
Comparative example 6:
the preparation method of the polysilicon functional film basically has the same specific steps as the embodiment 4, and the differences are that:
in the step 3), the etching and cleaning operations are as follows: and (3) carrying out etching cleaning on the substrate containing the oxide layer for 10s by adopting ultrasonic wave assistance with the power of 900W in the presence of potassium bromate at the temperature of 90 and the temperature, wherein the weight ratio of the potassium bromate in an etching medium is 0.075 percent, and the etching medium also comprises 2.5 percent by weight of hydrofluoric acid.
Test example 1:
deposition test of polysilicon functional films prepared by different preparation methods
The test method comprises the following steps: polycrystalline silicon functional films were prepared according to the preparation methods of examples 1 to 4 and comparative examples 1 to 4, thickness tests of the functional films were performed using ST2000-DLX film thickness tester, test data were obtained by averaging 5-point measurements, and growth deposition rates were calculated as shown in table 1.
TABLE 1 deposition Rate test results for different polysilicon functional films
The results show that the deposition rate differences of examples 1 to 3 are not significant, and the deposition rate of example 4 is slightly increased, which is probably because the etching cleaning operation is performed on the oxide layer by using ammonium fluosilicate and potassium bromate in example 4, so that the adverse effect of uneven grain size and thickness on the surface roughness of the deposited film is improved while the thickness and grain size of the film are uniform in growth, and the deposition rate is improved. Of comparative examples 1-4, comparative example 4 had the slowest deposition rate; the difference between comparative examples 2 and 3 is not significant and is improved compared with comparative example 4; the deposition rate of comparative example 1 was the fastest, but still significantly lower than that of example 1; the pulse cleaning can improve the cleanliness of the surface of the substrate and can also improve the deposition rate of the polycrystalline silicon film, and in addition, in the embodiment 1, the pulse cleaning is performed on the substrate in the presence of potassium fluotitanate and neodymium sulfate, so that the steric hindrance effect between the substrate and the precursor can be obviously reduced, the growth deposition rate of the polycrystalline silicon film is accelerated, and the production energy consumption and the cost are saved.
Test example 2:
roughness and surface test of polysilicon functional film prepared by different preparation methods
The test method comprises the following steps: the polycrystalline functional films were prepared according to the preparation methods of examples 1 to 4 and comparative examples 1 to 4, and the surface roughness of the samples obtained at different stages was observed and scanned using a keyence VK-9700 color 3D laser microscope. The results are shown in Table 2.
TABLE 2 roughness test results (unit: nm) for different surfaces under different preparation methods
The results show that the silicon-based substrates of examples 1-4 and comparative examples 1-4 had insignificant roughness difference before and after pulse cleaning, but had differences in roughness of the oxide layer and the polysilicon film, wherein the roughness differences of the oxide layer and the polysilicon film of examples 1-4 were insignificant; however, in comparative examples 1 to 4, the roughness values of comparative example 4 were all the maximum values; the difference between comparative examples 1 and 3 is smaller and is reduced compared with comparative example 4; the roughness of comparative example 2 was the lowest, but still significantly lower than that of example 1; in addition, in the embodiment 1, the substrate is subjected to pulse cleaning in the presence of potassium fluotitanate and neodymium sulfate, so that the increase of the surface roughness of an oxide layer can be inhibited, the surface roughness and the surface smoothness of the polycrystalline silicon film are further improved, the polycrystalline silicon film with low surface roughness and high flatness is obtained, and the quality and the yield of products are improved.
Test example 3:
warping degree test of polycrystalline silicon functional films prepared by different preparation methods
The test method comprises the following steps: the preparation methods of examples 1 and 4 and comparative examples 5 and 6 were used to prepare polysilicon functional films with a diameter of 200mm, and the warpage of the polysilicon thin film and the silicon-based substrates before and after the preparation was measured according to the automatic non-contact scanning method of the warpage test of the silicon wafer in GB/T32280-2015, and the results are shown in fig. 1.
Fig. 1 is a schematic diagram of warp changes before and after a polysilicon functional film and a silicon-based substrate in different preparation methods. The result shows that the warpage of the polysilicon functional film is respectively as follows: example 1 was 9.5 μm, example 4 was 3.6 μm, comparative example 5 was 8.3 μm, and comparative example 6 was 9.7 μm; the most varied warpage before and after the silicon-based substrate was comparative example 6, example 1, and comparative example 5 again, example 4, which varied the least; it is demonstrated that in the preparation method of embodiment 4, after etching and cleaning are performed in the presence of ammonium fluorosilicate and potassium bromate, the diffusion of reactants on the surface of the oxide layer can be synergistically increased, the warpage of the polysilicon thin film and the substrate can be effectively reduced, the warpage of the polysilicon functional film with the diameter of 100-200mm can be controlled below 5 μm, and the product quality can be improved.
Test example 4:
quality measurement of polycrystalline silicon functional films prepared by different preparation methods
The test method comprises the following steps: two polysilicon functional films with different thicknesses are prepared by the preparation methods of the examples 1 and 4 and the comparative examples 5 and 6 respectively
And
the thickness of the functional film was measured by using an ST2000-DLX film thickness tester, the surface roughness of the functional film was measured by the method of test example 2, and the crystal grain size was measured and calculated by X-ray diffraction spectroscopy. The results are shown in Table 3 below.
TABLE 3 quality measurement results of polysilicon functional films prepared by different preparation methods
The results show that after the functional film thickness of the example 1 and the comparative examples 5 and 6 is increased, the thickness uniformity of the film is reduced and is more than 1%, the thickness uniformity of the example 4 is kept to be less than 1%, and the functional film thickness distribution of the example 4 is uniform, so that the loss rate of subsequent processing is favorably reduced. In addition, as the thickness of the functional film increases, the grain diameter and the surface roughness of the film also increase, but the difference between example 1 and comparative example 5 is not significant and the increase is the largest; comparative example 6 times, example 4 had the least growth; it is shown that, in the preparation method of example 4, after etching and cleaning are performed in the presence of ammonium fluorosilicate and potassium bromate, the increase in the diameter of silicon film, which causes inconsistent grain diameter growth and rapid surface roughness growth, can be synergistically inhibited, the uniformity of grain size and distribution can be improved, the loss rate in subsequent processing operations can be reduced, and the production loss and cost can be reduced.
The above embodiments are merely illustrative, and not restrictive, and those skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention. Therefore, all equivalent technical solutions also belong to the scope of the present invention, and the protection scope of the present invention should be defined by the claims.
Claims (10)
1. A preparation method of a polysilicon functional film comprises the following steps:
providing a pretreated silicon-based substrate;
forming a silicon dioxide oxide layer on the substrate;
after the substrate containing the oxidation layer is subjected to alkali washing treatment, heating the substrate containing the oxidation layer to a deposition temperature; and the number of the first and second groups,
exposing the oxide layer-containing substrate to at least one group IV precursor and growing a polysilicon film using an LPCVD process;
wherein the pretreatment of the silicon-based substrate comprises a pulse cleaning step; the pulse cleaning is 20-30 cycles, the pulse time is 0.1-0.2s, and the cleaning time is 4-5 s.
2. The method for preparing a polysilicon functional film according to claim 1, wherein the method comprises the following steps: in the pulse cleaning step, the pulse medium is tetraethoxysilane, and the cleaning medium is NH4F. HF, potassium fluotitanate and neodymium sulfate to prepare a solution with the pH value of 4.5-5.
3. The method for preparing a polysilicon functional film according to claim 2, wherein: NH in the cleaning medium4F. HF, potassium fluorotitanate andthe weight ratio of the neodymium sulfate is 10:10:0.1-0.3: 0.1-0.5.
4. The method for preparing a polysilicon functional film according to claim 1, wherein the method comprises the following steps: in the pulse cleaning step, the temperature of the pulse medium and the cleaning medium is 180 ℃ and the temperature of the substrate is 200 ℃ and 350 ℃.
5. The method for preparing a polysilicon functional film according to claim 1, wherein the method comprises the following steps: the heating of the substrate comprising the oxide layer to the deposition temperature is heating the substrate to 350-.
6. The method for preparing a polysilicon functional film according to claim 1, wherein the method comprises the following steps: the LPCVD process conditions are as follows: the pressure is 25-75Pa, the deposition temperature Td is 600-650 deg.C, and the precursor flow rate is 300-1500 sccm.
7. The method for preparing a polysilicon functional film according to claim 1, wherein the method comprises the following steps: the preparation method also comprises the step of carrying out heat treatment on the polycrystalline silicon film prepared by the LPCVD process; the operation steps of the heat treatment are as follows: heating to 950-1040 ℃ at the speed of 150-200 ℃/min, and then annealing for 60-75 min.
8. The polycrystalline silicon functional film produced by the production method according to any one of claims 1 to 7.
9. The polysilicon functional film according to claim 8, wherein: the thickness of the polysilicon functional film is
And when the thickness uniformity in the sheet is not higher than 1.5%.
10. Use of the polycrystalline silicon functional film produced by the production method according to any one of claims 1 to 7 for producing an electronic device.
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| KR20050050820A (en) * | 2003-11-26 | 2005-06-01 | 삼성에스디아이 주식회사 | Method of washing using pulse zet type cleanning solution supply and devices for performing the same |
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